Just post a question related to a location on the site or its smartphone app counterpart. Any user who's checked into that location (via Foursquare, Facebook Places, Gowalla and others) will be notified. If they answer, you'll receive their response immediately.

Even Foursquare users who don't use Localmind are available for questions.

Whose idea: Lenny Rachitsky

Why it's brilliant: Say you're headed to your favorite bar. Not only can you see who's there, you can find out if there's traffic nearby.